This invention relates to the method and apparatus for indicating roller wear in a media handling device. Such structures of this type, generally, employ the use of variable inductance to determine roller wear. The media transport roller has a non-conductive surface with a conductive core. Located just above the conductive core is a rod containing a power coil that is driven by AC excitation and a pick-up coil. The pick-up coil is connected to circuitry that measures the inductance. As the media transport roller wears, the conductive core moves closer to an inductive pick-up unit. The measured output voltage from the pick-up unit depends upon the distance between the core and the pick-up unit. This inductance change can then be correlated to media transport roller wear and relayed to the user through the use of an LED or other similar types of graphical/numerical displays.
Prior to the present invention, as set forth in general terms above and more specifically below, it is known, in the media handling device art, to make use of a device for determining roller wear. Exemplary of such prior art is U.S. Pat. No. 6,055,047 (""047) to A. Schweizer et al., entitled xe2x80x9cDevice for Determining the Degree of Wear of a Paper Transport Roller.xe2x80x9d The ""047 reference discloses a paper transport roller which comprises two layers having different degrees of reflection for electromagnetic radiation. When the outer layer is worn, the degree of reflection of the surface of the paper transport roller changes and the user is signaled that paper transport roller must be replaced. However, if a foreign object becomes attached to the transport roller of the ""047 reference, this foreign object could adversely affect the reflection characteristics of the device. Also, if the paper transport roller does not wear evenly, one edge of the roller may have a different degree of reflection than the other edge of the roller and, possibly, adversely affect the reflection characteristics of the device. Therefore, a more advantageous paper transport roller wear indication system, then, would be presented if the system did not have to rely on a paper transport roller which comprises two layers having different degrees of reflection.
It is apparent from the above that there exists a need in the art for a paper transport roller wear indication system which is lightweight through simplicity of parts and uniqueness of structure, and which these equals the wear indication characteristics of the known paper transport roller wear indication systems, but which at the same time employs variable inductance which will alert the user to the worn condition of the paper transport roller. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.
Generally speaking, this invention fulfills these needs by providing a method for indicating media transport roller wear, wherein the method is comprised of steps of: creating a variable inductance between a pick-up unit located substantially adjacent to a media transport roller and a conductive surface located on the roller; and indicating an amount of roller wear by measuring a change in the variable inductance.
In certain preferred embodiments, the pick-up unit consists of a power coil that is driven by AC excitation and a pick-up coil. Also, the media transport roller conductive surface is a conductive core upon which the media transport roller rotates. Finally, the method further includes step of tracking the rotations of the media transport roller such that the power coil would not need to be activated until the media transport roller had completed a predetermined number of rotations.
In another further preferred embodiment, the wear of the media transport roller can be accurately detected so that the user can be alerted that the roller needs to be replaced and/or serviced.
The preferred media transport roller wear indicating system, according to this invention, offers the following advantages: lightness in weight; ease of assembly and repair; excellent roller wear indicating characteristics; good stability; good durability; and excellent economy. In fact, in many of the preferred embodiments, these factors of lightness in weight, ease of assembly and repair, excellent roller wear indicating characteristics, and excellent economy are optimized to an extent that is considerably higher than heretofore achieved in prior, known media transport roller wear indicating systems.
The above and other features of the present invention, which will become more apparent as the description proceeds, are best understood by considering the following detailed description in conjunction with the accompanying drawing figures, wherein like characters represent like parts throughout the several views and in which: